Dynamic braking device for idly-running motors



March 17, 1931. A. .BESSLER DYNAMIC BRAKING mzvzcn' FOR IDLY RUNNING MOTORS s Sheets-Sheet 1 Filed which 51, 1924 March l7, 19 31. BESSLER 1,796,555

' DYNAMIC BRAKING DEVICE FOR IDLY RUNNING MOTORS Filed March 31, 1924 3 sheets sheet 2 v Fig.5;

3' 1 f d d d e e g .e3e# I A. BESSLER March 17, 1 931.

DYNAMIC BRAKING DEVICE FOR IDLY RUNNING MOTORS 3 Sheets-Sheet 5 Filed March 51, 1924 I shaft is locked and the 1 connected to its Patented Mar. 17, 1931 UNITED STATES PAT'E NT OFFICE SCHAFT, OF ESSEN-ON- THE-RUHR, GERMANY DYNAMIC BRAKING DEVICE FOR IDLY-RUNNING MOTORS Application filed March 31, 1924, Serial No. 708,265, and in Germany larch 31, 1928.

The invention relates to operating mechanisms for cash registers, calculating machines and the like of the kind in which at the end of an operation of the machine the coupling between the driving motor and the operating shaft of the machine is released, the operating circuit supplying the motor is interrupted. A simple interruption of the circuit suffers from the drawback that the motor produces a disturbing noise in slowing down without load. If, as it has been proposed, the main is connected to the motor inversely and the counter-current interrupted at the beginning of the reverse rotation of the motor, this latter, it is true, will quickly come to rest, but other disadvantages will arise in this case, in particular high mechanical and electrical stresses. In order to obviate them, a switch method is made use of according to the invention, ,which is known with motors permanently working in loaded state-and in which method the armature of the motor,

after beingdisconnected from the main, is exciting winding in inverse switching direction. With this end in view the: invention consists of the arrangement, construction and combination of parts to be hereinafter described and particularly pointed out in the appended claims. In order to allow of the invention to be more readily understood, an embodiment of the same will now be described in detail, by way of example. In the drawing Fig. 1 is an elevation of the mechanism in position of rest,

Fig. 2 is a correspondin top view,

Fig. 3'is the section on ine 3-3 of Fig. 2, seen from the left,

Fi 4 is the section on line 4-4 of Fig. 2, seen Irom the right;

5 and 6 are elevations illustrating the mechanism in different working positions;

Fig. 7 shows a throw-over switch and its wire connections in position of rest, and

Fig. 8 shows it in working position.-

A denotes themain operating shaft of the machine which has mounted on it for free rotation a worm wheel a in mesh with a worm, not shown, mounted on the motor shaft. Beside the worm wheel a there is arranged on disks 0 and G,

the shaft A a disk t Fi s. 2 the 3, which forms part of a clutch the other parts of which areJodged within the worm wheel a. r

This clutch is known per se and needs no description in detail. It acts in a manner such as to cause the Worm wheel a which is rotated by the motor in the direction of the arrow, the shaft A as long as the disk a is not hindered from taking part-in the rotation of said worm wheel. When the rotation of the disk a is stopped, the worm wheel a will be uncoupled from the shaft A. The disk at carries a lateral lug a see particularly Fig. 3, adapted to co-operate with a laterally bent lug b of a locking lever B. This lever B is pivoted on the axle I) mounted on the frame of the machine, and is acted upon by a spring I) and a thrust bar I). This latter is connected to it b means of a pin b engaging a slot 6 of the ar 6.

I) The free end of the lever B shows a surface anism, Fig. 1 abuts a ainst a lateral lug 0 of a locking disk on d y fixed on the shaft A. Besides this disk there is arranged on the shaft A a switch disk C which is adapted to rotate within certain limits and tends to turn a spring a, wound on the shaft A,in the direction of the arrow, Fig. 1. The rotatingmotion of the disk 0 with respect to the disk C, and therewith tothe shaft A, is limited by a pin 0 fixed on the disk C and engaging a slot a concentric with the shaft A, of the switch disk C of rest the lug b the switch disk eral lug 0 fixed in this position of the locking lever B locks on said disk, the pin 0* lying v in the lower end of the slot 0", Fig. 1. Furthermore, in this position a notch 0 provided on the riphery of the disk 0 and a notch c rovi ed on the periphery of the disk 0 are situated beside one another. A roll d abutsagainst the periphery of the said roll beingeplvoted at the apex of a rectangularly bent ll crank lever When the mechanism is in position G by abutting against a lat- Fig. 1, to automatically couple itself to y which in the position of rest of the mechslever is adapted to swing about a pin d on the frame of the machine and shows a nose dwhich projects beyond theperiphery of the roll al and is adapted to co-operate upon an insulating piece e with the lateral lug c of the disk C. The free end d of the bell crank lever I) rests connecting two yielding contact bars E E Figs. 7- and 8. These contact bars tend to lift the end at of the lever D so that the roll al engages the notches and a when the latter are opposite the roll and the lug c is out of the path of the nose d.

The contact bars E E are conductively connected to the exciting winding F of the motor. In the position of rest, Fig. 7, of the mechanism, these bars abut against contact pieces 6, e to which the armature of the motor is connected. In the working position they abut against contact pieces e, e the piece 6 of which is connected through the starting resistance H to the positive pole of the main,

-' while the piece 6* is connected to the contact piece e. The conductor connected to the nece'e leads to the negative pole of the menu.

The described mechanism works as follows:-

In the position of rest of the mechanism, Fig. 1, the surface I) of'the locking lever B ,abuts against the lug c of the locking disk The circuit closed in this wayis indicated in :pring a Fig. 7 by full lines. The positive conductor of the main is interrupted at e and the motor is not sup lied with current.

When the operation of the machine is initiated by depressing a special key or the like, the locking lever B will be displaced so as to take the position of Fig. 5. When this takes place the three lugs 0 c, a are released by the surface I) and the lug b of the lever B. Upon releasing the lu c the switch disk C suddenly rotates un er the action of the so far in thedirection of the arrow at theupper end of the slot 0 engages the pin 0 and the roll d is Pressed out of the notch 07 by the cam-like li ting surface of the notch a. The endd of the lever D so depresses the contact bars E E that they come into contact with the contact pieces'e -e and establish a circuit as illustrated in Fig. 8.-

This'current flows from the +pole through H, e, E, F, E, e,.G to the pole and t e motor will start. As the disk a is allowed to partake in the rotation of the worm wheel a, the colipling between the worm wheel and the shaft is effected sothat the shaft A and the disk C rotate also. Consequently the smooth portion of the periphery'of the disk C will come opposite the roll 11 and the contact bars E E remain locked in their depressed position.

Towards the end of the operation of the machine the locking lever B is brought by the bar b back into locking position where its lug b firstly stops the lug 0 of the switch a disk C whilst the spring 0 1s tensioned again. Then also the lug a of the disk a is stopped by the-lug b of the lever B whereby the uncoupling of the worm wheel a, still continuing to rotate, from the shaft A is caused. Shortly thereafter, due to the inertia of the shaft the lug c of the disk G hits the surface I) of the locking lever B so that the operating shaft A is stopped after having completed one revolution precisely. In the meantime the notches 0" 0 had come to lie again opposite the roll d and the latter would have been able to successively engage the notch c" as the upper edge of this notch moves upwards. But,

in order to secure a quick reversing of the contact bars so that formation of sparks is obvlated, the lock 0 (i acts in a manner such as to cause the roll (1% to engage the notches only when it is op osite them with its entire diameter. Upon this engagement by the roll taking place shortly before the operation of the machine is completed, the contact bars E E abut against the upper contact pieces e e whereby the switch position of rest shown in Fig. 7, is restored. The motor is thus cut off from the main and slows down without load by its inertia, since it has'already been uncoupled from the operating mechanism of the machine and this;mechanism has been locked. As will be seen froml Fig. 7, the armature of the motor is connected in series with the exciting winding F and this in a sense inverse to that of the working connection, Fig. 8. A current will therefore arise in the armature owing to the eounter-electromotive force converted into-electromotive force act-. ing as in a generator, which current flows in the same direction through the field winding F as in the working connection of Fig. 8. Consequently this current provokes a powerful braking held in which the armature will quickly come to rest. As in braking the armature the current decreases down to zero and in the state of rest of the motor no current at all flows through the parts in question, the connections illustrated in Fig. 7 may remain also for the position of rest of the described mechanism.

Claims:

1. In a machine ofthe class described. a driven shaft, an electromotor, a clutch between said driven shaft and said electromotor, means for controlling said clutch, means for arresting said driven shaft in a limit position, an armature and an exciting winding in said electromotor, a switch, circuit connections between said switch and said armature and exciting winding whereby said switch is adapted to short-circuit the armature solely throu h the exciting winding, and connections tween said clutch-controlling and arresting means and said switch, whereby said switch short-circuits the armature solely 5 through the exciting winding upon said drivenshaft having attained its limit position.

2. In a machine of the class described, a driven shaft, an electromotor, aclutch between said driven shaft and the electromotor, means for throwing in said clutch, means for throwing out said clutch, means for arresting said driven shaft in a limit position, an electric switch, an armature'and an exciting winding in said electromotor, circuit connections between said switch and the armature and exciting winding, whereby the switch in a first position is adapted to short-circuit the armature solely through the exciting winding and in a second position to connect the armature in series with the exciting winding and a main, and connections between said clutch controlling means and said switch whereby the latter is brought into its first position upon the actuation of said throwing-out means and into its second position through the actuation of said throwing-in means.

The foregoing specifications signed at Cologne, Germany, this 4th day of March,

AUGUST BESSLER. 

